Since narrow frequency band communication signals are easily detected, jammed, etc., military communication systems utilize bandspread communication signals. However, in a military theater of operation, unfriendly forces intentionally interject non-Gaussian interference into the radio transmission spectrum which can interfere with the reception of even bandspread signals. Additionally, such "intentional" interference generally dominates the transmission signal as well as any Gaussian noise associated therewith.
Prior art interference suppression systems have typically applied adaptive filtering techniques to suppress interference from bandspread communication signals. One of the most effective techniques to date uses an adaptive Wiener filter to estimate the phase properties of the interference. See, for example, "Adaptive Signal Processing" by Widrow and Stearns, Prentice Hall, 1985. While this approach is straightforward, the calculations required are tedious and can become quite complex. Furthermore, Wiener filters are also susceptible to non-relevant broadband noise because their phase properties cannot be predicted.
Thus, a need exists for a simple and effective method of suppressing interference from bandspread communication signals. Accordingly, an object of the present invention is to provide a method and apparatus for suppressing interference from bandspread communication signals whenever the interference dominates the signal being received. Another object of the present invention is to provide a method and apparatus for suppressing interference from bandspread communication signals that is easily adapted to existing radio receivers. Still another object of the present invention is to provide a method and apparatus for suppressing interference from bandspread communication signals that is less affected by non-relevant broadband noise than adaptive Wiener filters.